1. Technical Field
The present invention relates to an electric power supply apparatus for a display system and, more particularly, to an apparatus and a method for saving electric power in a display system in which, when the display system is turned to an off mode, total electric power consumption is reduced to a range wherein the display system can be operated through a reduction of an on-duty time period of a pulse width modulation (PWM) pulse by using a charging/discharging device of large capacitance.
2. Related Art
Most display systems appearing on the market recently are equipped with an electric power-saving mode. The power-saving mode proceeds sequentially through a normal mode, a suspend mode, a standby mode, and an off mode, depending on whether or not horizontal and vertical synchronization signals from a video card built into the main body of a computer are inputted.
The off mode is applied when neither the horizontal nor vertical synchronization signals are inputted from the video card in the main body of the computer.
Specifically, the off mode is used to minimize electric power consumption in a display system by cutting off electric power supplied to all parts of the computer when a user does not use the display system, that is, when it is determined, as a result of a detection process, that neither horizontal nor vertical synchronization signals are inputted.
In the off mode, a microcomputer is still supplied with sufficient electric power to enable the display system to be turned to the normal mode when horizontal and vertical synchronization signals are inputted from the video card in the main body of the computer.
In such a system as generally described above, the power savings achieved are limited, even when the system is placed in the off mode. This is due to the fact that, even when in the off mode, the system must provide power to the microcomputer so that it can continue to monitor the status of a signal input from the computer main body in order to determine whether horizontal and vertical synchronization signals are being inputted from a video cord in the computer main body. Since, in such a system as described above, power must be provided to the microcomputer at all times, satisfactory power savings cannot be achieved.